Intersection over Union (IoU)

What is Intersection over Union (IoU)?

Intersection over Union (IoU) is the ratio of overlap area to union area between a predicted bounding box and a ground-truth box—the core localization metric for object detection.

Thresholds like 0.5 IoU define true positives in VOC/COCO-style evals. Report mean average precision (mAP) across IoU thresholds for a fuller picture.

Further reading

Authoritative reference: Wikipedia: Jaccard index (IoU).